Bogging off the startline

db · Post by db » Mon Aug 08, 16 11:56 pm

I was wondering if increasing shooter size would help my launch.
Before I start experimenting, do I keep primary and secondary the same?
It's also occurred to me that as I wa launching at 4-5000 I bet I need to change the pump cam position from hole 1 to 2.

Pete · Post by **Pete** » Tue Aug 09, 16 7:50 am

Most of the pump shot is done by then.

When you are at the track you may have to slacken off your pump adjustment so it delays the shot.

db · Post by db » Tue Aug 09, 16 9:30 am

So is there any point playing around with pump cams or shooters?
I've tried swapping pump cams before and not really achieved anything but confusion...
I've never changed shooters, they're both 31.

Blue · Post by **Blue** » Tue Aug 09, 16 12:55 pm

What you can do is mess with the secondary pump, it's unlikely that has shot it's load by then. Bigger shooter, more aggressive pump cam and ultimately a 50cc pump are things you can experiment with. The other thing you can experiment with is the power valve, the sooner that opens the quicker it enriches the mixture, if it's a big bog that might be the only way to get rid of it.

Mick · Post by **Mick** » Tue Aug 09, 16 3:11 pm

Are you using jet extensions ?

db · Post by db » Tue Aug 09, 16 3:51 pm

Yes to jet extensions.
Yes to 50cc sec pump.
Yes it's a big bog!

I'm running a 4.5pv but I suspect it opens at idle sometimes as vac at idle is an unsteady 5.

I have a 2.5 I was about to try but that's going the wrong way to cure the bog isn't it?

Blue · Post by **Blue** » Tue Aug 09, 16 5:24 pm

In that case try an 8.5, it will be open at idle but you can lean it off with the idle screws. I've had a couple of instances were I had a bad bog and very low idle vacuum, worked in both cases.

Pete · Post by **Pete** » Tue Aug 09, 16 6:42 pm

Are you WOT on a Rev limited or foot brake and watching the rev counter?

db · Post by db » Wed Aug 10, 16 12:34 am

Ta Blue I've heard of that trick before. I'll give it a go 😊
Watching the revcounter with the clutch let out as far as I can without moving Pete, I don't have enough feet to hold the brake

Pete · Post by **Pete** » Wed Aug 10, 16 8:02 am

Line lock, mate.

On a race car you would have a 1st stage Rev limiter so you would already be at WOT, so the pumps would not work at all, hence the question.

I would back off both pump arms to delay the shot and try again. You could have a rich bog (but I doubt it) so at least this would prove it.

Make sure there is still sufficient cam profile to obtain a decent pump, you may have to bend the arm a bit.

db · Post by db » Wed Aug 10, 16 4:11 pm

Ta Pete.
I think I'd need a bit more practice to add the linelok into the things to remember on the startline, it's bewildering enough already!

I'll try the pv trick as that's easy to try out. Then I'll have a play around with the pump arms, cams, etc

Blue · Post by **Blue** » Fri Aug 12, 16 4:01 pm

Linelock is easy as long as you have the button on the shifter or the steering wheel. You could even do something fancy like releasing it via a micro switch on the clutch pedal.